London Calling: Google Doesn't Take Electricity for Granted

Change is never essay, but the need to rework electrical distribution infrastructure to make it ready for smart grid operations presents a compelling reason we should.

It is very easy to assume that just because things have always been done a certain way, at least in your own lifetime, they always will be done that way. One example is electricity distribution, and it is interesting to consider whether there are parallels between electricity distribution at the largest possible scale -- the national and international electricity grids -- and at the small scale on the printed circuit board and the backplane?

In the electricity grid and over long distances, distribution is typically done at more than 100kV using alternating current, with down conversion to tens of kilovolts AC in the distribution grid, then to hundreds of volts for some industrial supplies, and finally down to 120V or 240V for domestic users.

It has always been so, and of course, the more that infrastructure gets built, the more incentive there is to stay with the present system. But needs change, and so the need to rework electrical distribution infrastructure to make it ready for smart grid operations provides an opportunity for change.

It turns out that high-voltage DC (HVDC) offers a number of potential advantages for distribution. And the higher the voltage, the smaller the current. For example, HVDC does not suffer from energy losses due to changing line capacitance. Also, thinner conductors can be used, because HVDC does not suffer from the skin effect in conductors. Fewer conductors are required than for an AC line, because there is no need to support multiple phases. As a result, losses per 1,000 kilometers are usually less for HVDC than for HVAC, though costs for conversion equipment at either end also have to be considered.

Of course, because many of those conductors are already in place, the application of DC transmission could be used to increase energy transport without rolling out additional long-distance lines. This could accommodate the smart-grid control we are told we need so much.

The main advantage of HVDC, and the reason it rules for undersea/underground cables is that it requires less insulation. HVAC must be insulated to peak line voltage equal to 1.42 times the rated line voltage spec.

For overground lines this is not a problem---just space the lines out a little more. For a compact cable however this leads to huge cost savings.